My experience in a subtropical climate in Mexico (temp range - 0C to 35C, high humidity): uninvited BSF invaded my red wiggler habitat and persisted with no intentional support from me. The larvae went everywhere, especially before/after a big rainstorm. They were much more prolific and hardier than the red wigglers. I never tried to get rid of them, but I doubt it would have been possible. I was also never able to contain them, but I never tried one of the commercial bin options.
I would venture a guess that perhaps your genetic stock was not so great, or perhaps there was not enough genetic diversity to adapt to your conditions, or maybe you're efforts to create an ideal environment are backfiring somehow. In your position, I would get some more BSF (from multiple sources if possible) and try again. I would try less environmental control, just put them outside in a semi-sheltered area - no fan or direct sun or anything like that. Let natural selection take a shot at it, and if that doesn't work I guess I would look at different insect options.
Good Luck!
